These "competitive exams" are a staple of anime writing but are always stupid. So you get a year with 5 good teams, only 3 will qualify, wasting two good teams. Then you get a year with 5 mediocre teams, and you get 3 mediocre teams through. It's just stupid.
In addition, clearly each urararara has to work for herself later on. So a team exam seems like it'd far too easily allow somebody to slip through that doesn't have any level of skill.